Grantee Research Project Results
Final Report: Acute and Developmental Toxicity of Metal Oxide Nanoparticles in Fish and Frogs
EPA Grant Number: R832842Title: Acute and Developmental Toxicity of Metal Oxide Nanoparticles in Fish and Frogs
Investigators: Theodorakis, Christopher , Carraway, Elizabeth , Cobb, George
Institution: Southern Illinois University - Edwardsville , Clemson University , Towson University
EPA Project Officer: Aja, Hayley
Project Period: October 24, 2005 through October 24, 2008
Project Amount: $375,000
RFA: Exploratory Research: Nanotechnology Research Grants Investigating Environmental and Human Health Effects of Manufactured Nanomaterials: A Joint Research Solicitation - EPA, NSF, NIOSH (2005) RFA Text | Recipients Lists
Research Category: Human Health , Safer Chemicals , Nanotechnology
Objective:
The long-term goals of this research are to assess ecological hazards and risks - and provide recommendations for preventing ecological damage - from application of emerging technologies. The objective of this research is to determine the relative environmental hazard of selected metal oxide nanoparticles (Fe2O3, ZnO, CuO, and TiO2) to fathead minnows (Pimephales promelas) and African clawed frogs (Xenopus laevis). The central hypothesis is that exposure to metal oxide nanoparticles will elicit acute and chronic toxicological effects in these species. The rationale is that once the toxicological endpoints have been determined, this information can be used to determine the degree to which these materials pose an ecological hazard, to formulate regulatory benchmark concentrations for effluents and receiving waters, and to calculate probabilistic risk assessments for populations of fish and amphibians. The principal investigators are uniquely qualified for this research because of their experience in aquatic toxicity testing, long history of work with environmental fate of metals, manufacture and environmental application of nanoparticles, and because they have developed a synergistic, multidisciplinary team with experience in aquatic and molecular toxicology, environmental chemistry, and engineering science. The specific aims of this research are to determine:
- Acute toxicity of metal oxide nanoparticles. This will be accomplished by conducting standardized short-term toxicity and tests. The working hypothesis is that suspensions of nanoparticles will affect growth and survival of fish and frogs.
- Developmental and chronic toxicity of metal oxide nanoparticles. This will be accomplished by conducting fathead minnow early life stage (ELS), frog embryo teratogenicity assay, Xenopus (FETAX), and 10-week chronic Xenopus exposures. Endpoints will be rate of development, growth, survival, and occurrence of developmental abnormalities. The working hypothesis is that developmental effects will occur at concentrations below those seen for acute lethality.
Summary/Accomplishments (Outputs/Outcomes):
1) Acute toxicity
Xenopus laevis
This study examined the effects of ZnO, TiO2, Fe2O3, and CuO nanoparticles (20-100 nm) on amphibians utilizing the Frog Embryo Teratogenesis Assay Xenopus (FETAX) protocol. Nanoparticles were dispersed in reconstituted moderately hard test solutions. These 96-h exposures caused no mortality in static renewal exposures containing up to 1000 mg/L for TiO2, Fe2O3, CuO, and ZnO, but did induce developmental abnormalities. Spinal and gastrointestinal abnormalities were observed in CuO and ZnO nanoparticle exposures. An EC50 of 10.3 mg/L ZnO was observed for total malformations. The minimum concentration to inhibit growth of tadpoles exposed to CuO or ZnO nanoparticles was 10 mg/L.
Fathead minnows
The objectives of this research are to determine the environmental hazard associated with selected metal and metal oxide nanoparticles (TiO2, ZnO, CuO, Cu, and Fe2O3), in terms of acute toxicity to fathead minnows (Pimephase promelas). The hypotheses were that nanoparticle exposure will affect the survival, growth, development, and egg hatchability of these organisms in a dose-dependant fashion, and differences in relative toxicity (LC50) of these nanoparticles coincide with the relative toxicity of their soluble salts or oxides. Fathead minnows were exposed to metal oxide nanoparticles during 96 hour acute toxicity tests. The 96-h LC50 for CuO, Cu, and Fe2O3 were 0.662, 0.009, and 22.5 mg/L, respectively. Acutely toxic effects of the other nanoparticles were not seen at concentrations up to 1000 mg/L.
The data suggest that iron oxide nanoparticles are moderately toxic, copper oxide nanoparticles are toxic, and copper nanoparticles are very highly toxic to fathead minnow larvae. Copper oxide and especially copper nanoparticles are toxic at environmentally relevant concentrations. The LC10 and LC50 concentrations for iron oxide may not be environmentally relevant except at sites with heavy contamination. Thus, the environmental hazard of these three nanoparticles decreases in the order of Cu > CuO > Fe2O3. Because Cu nanoparticles are so much more toxic than CuO, it is unlikely that the majority of the nanoparticles in the Cu were oxidized to CuO, although there may have been a coating of CuO at the surface of the nanoparticles. The data do not, however, indicate that TiO2 or ZnO are environmental hazards to fathead minnows.
2) Developmental and chronic toxicity
Xenopus laevis
Zinc oxide nanoparticles (40-100 nm) were used to dose Xenopus laevis tadpoles throughout metamorphosis to determine the effect of metal oxide nanoparticles on development. Nanoparticles were dispersed via sonication methods into reconstituted moderately hard water test solutions. A flow-through system was utilized to decrease the likelihood of the depletion in ZnO concentration. Exposure to 2 mg/L ZnO nanoparticles significantly increased mortality incidence to 40% and negatively affected metamorphosis of Xenopus laevis. Tadpoles exposed to 2 mg/L ZnO nanoparticles developed slower as indicated by tadpoles with an average stage of 56 at the conclusion of the study which was significantly lower than the stages of control tadpoles. No tadpoles exposed to 2 mg/L of ZnO nanoparticles completed metamorphosis by the conclusion of the study. Tadpoles exposed to 0.125 mg/L ZnO nanoparticles experienced faster development along with larger body measurements indicating that low dose exposure to ZnO nanoparticles can be beneficial to growth and metamorphosis of Xenopus laevis.
This study has shown that Xenopus laevis exposed to higher concentration (i.e. 1 and 2 mg/L) ZnO nanoparticles experienced an increase in mortality and slower development which produced smaller organisms. Conversely, exposure to 0.125 mg/L of ZnO nanoparticles caused tadpoles to develop faster and with larger body size compared to control tadpoles. Therefore, we conclude ZnO nanoparticles released into aquatic ecosystems in high concentrations could have detrimental effects on aquatic organisms for instance amphibians. However, control of ZnO nanoparticle release could reduce or eliminate the detrimental effects of ZnO nanoparticle toxicity to aquatic vertebrates.
Copper oxide nanoparticle exposure has proven to be toxic to many aquatic organisms with acute exposure, yet there is no information on the effect of prolonged exposure to CuO nanomatieral. Developmental toxicity of CuO nanoparticles was investigated by conducting a two week subchronic exposure and a long term developmental exposure throughout metamorphosis. The subchronic exposure caused mortality in all evaluated CuO nanoparticle concentrations, and significant growth effects occurred with 2.5 mg/L CuO exposure. Chronic developmental exposure of 0.3 mg/L CuO nanoparticles caused significant mortality and affected the rate of metamorphosis by slowing stage progression. Exposure to lower concentrations of CuO nanoparticles induced increased stage progression and body measurements, indicating that low dose exposure can have beneficial effects on metamorphosis. Tadpoles exposed to 0.15 mg/L CuO nanoparticles experienced similar stage progression and growth as control tadpoles for the majority of exposure.
The results of this study suggest that exposure to high concentrations of CuO nanoparticles (0.3-2.5 mg/L) can negatively affect amphibians by decreasing survivability as well as inducing physiological stresses which can produce smaller organisms. Our study has shown that exposure to relatively lower concentrations of CuO nanoparticles (0.01875-0.15 mg/L) can also benefit amphibian development and allow tadpoles to complete metamorphosis faster and with larger body sizes than control organisms. In conclusion, CuO nanoparticles can be toxic to a variety of aquatic organisms including Xenopus laevis and release of CuO nanoparticles should be controlled to reduce the risk of damaging aquatic ecosystems.
Fathead minnows
The objectives of this research are to determine the environmental hazard associated with Fe2O3, CuO nanoparticles in terms of acute and chronic toxicity to fathead minnows. The hypotheses were that nanoparticle exposure will affect the survival, growth, and development of these organisms in a dose-dependant fashion. Fathead minnows were exposed to metal oxide nanoparticles during 28-day chronic toxicity tests in a flow-through system. Endpoints included survival, growth, and developmental abnormalities. It was found that exposure to metal oxide nanoparticles increased mortality, decreased growth, and induced developmental defects (spinal deformities). In general, both growth and mortality increased at Fe2O3 NP concentrations ≥ 0.35 mg/L (nominal concentration). Deformities were not observed for Fe2O3 nanoparticles. Overall, growth was inhibited and mortality increased at 65 µg/L CuO NP, and there was an increased number of deformities (spinal curvature) for CuO NP concentrations ≥ 32.5 µg/L, as compared to control.
Conclusions:
The data support the hypothesis that these nanoparticles are a hazard with chronic exposures and at environmentally relevant concentrations (< 1 mg/L), especially CuO and Cu. For CuO, percent deformities was the most sensitive indicator of toxicity, but for Fe2O3, growth and mortality were equally sensitive. Although most of the data indicated a detrimental effect of chronic nanoparticle exposure on fitness parameters, iron seemed to have a stimulatory effect on growth. In fact, there seemed to be a positive association between growth and mortality when exposed to Fe2O3. I.e., when iron oxide NP-exposed fish grow faster, they die in greater numbers.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 13 publications | 1 publications in selected types | All 1 journal articles |
---|
Type | Citation | ||
---|---|---|---|
|
Nations S, Wages M, Cañas JE, Maul J, Theodorakis C, Cobb GP. Acute effects of Fe2O3, TiO2, ZnO and CuO nanomaterials on Xenopus laevis. Chemosphere 2011;83(8):1053-61. |
R832842 (Final) |
Exit Exit |
Supplemental Keywords:
Water, animal, ecosystem, aquatic, biology, Southwest, Midwest., Health, Scientific Discipline, ENVIRONMENTAL MANAGEMENT, Environmental Chemistry, Health Risk Assessment, Risk Assessments, Biochemistry, Risk Assessment, nanochemistry, animal model, bioavailability, nanotechnology, nanomaterials, animal bioassays, nanoparticle toxicity, analysis of chemical exposureProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.